Inflation doesn't explain reducing the included traffic from 20TB to 1TB while simultaneously increasing prices. This is a much more dramatic change than what inflation would justify.
Things are rarely priced at actual face value.
You purchase a 10Gb/s firewall for $100,000 - you will not be using 10Gb/s traffic for the lifespan of this device.
Applying this to Hetzner:
You sell a service with X bandwidth included free because you know that only Y% is only ever used on average.
Now people exploit the X allowance - spinning up new virtual machines to multiply this already generous allowance to get unlimited bandwidth for a fee 1/10000th of other commercial offerings. Your Y% costing is now completely invalid.
You reduce the allowance 20x to mitigate this.
I can't blame Hetzner at all for this, especially when Google/Amazon/Microsoft are printing money with their insane bandwidth costs. You know they are insane when they then change the rules to say it's completely free if you are migrating to a different provider - suddenly it doesn't cost anything at all for egress? Oh, it was actually upcoming monopoly investigations that might have taken a dim view...